Field of the Invention
The present invention is directed in general to power supplies. In one aspect, the present invention relates to test circuit for a switched mode power supply controller.
Description of the Related Art
In switched-mode power supplies (SMPS), a switching regulator is used to efficiently convert an input voltage to a desired output voltage. Typically, a switching regulator includes a DC/DC controller and a power section with drivers. There are several kind of switching regulators, including boost converters, buck converters, and buck and boost converters. The control circuitry may have voltage mode feedback or current mode feedback, and may use different types of compensation to generate the duty cycles for the power section. FIG. 1 is a simplified circuit diagram illustrating a switched mode power supply 100 which includes an input voltage Vin, an output voltage Vout, a controller circuit 110, and a buck-type DC/DC converter which converts an input voltage Vin to an output voltage Vout at a regulated value over the entire range of Vin, where Vin is greater than Vout.
While there are a variety of designs that are suitable for implementing DC/DC converters, the depicted buck-type DC/DC converter is constructed with passive filtering components, including an inductor 106 coupled between a capacitor 107 and rectifier 108. In addition, a controller unit 110 applies a gating pulse width modulation (PWM) signal 104 to a switch 103 which couples the input voltage Yin across the capacitor 107 and rectifier 108 to charge the inductor 106, thereby generating an output voltage Vout across the load 102. The depicted controller unit 110 includes a compensator 112, a saw wave generator 114, and a comparator 116. Due to the double complex pole introduced by the LC elements 106, 107, the compensator 112 generates a compensated error feedback signal 113 by introducing gain and phase lead to the feedback Vout signal 101 for achieving loop stability, improved bandwidth, and high DC gain. The saw wave generator 114 generates a saw wave clock signal 115 which is supplied to the comparator 116. The comparator 116 compares the compensated error feedback signal 113 and saw wave clock signal 115 to generate a pulse width modulation (PWM) signal 104 which drives the switch 103.
Further limitations and disadvantages of conventional technologies will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings and detailed description which follow.